The present invention relates to industrial process control. More specifically, the present invention relates to controlling processes which are used to manufacture paper or paper pulp.
In a control system, including controls systems which are used to control paper and paper pulp manufacturing, the state of a process is monitored by measuring xe2x80x9cprocess variables.xe2x80x9d A process variable refers to a variable which is related to the condition of the process such as a flow rate, a level, a temperature, a pressure, etc. Based upon the measured process variable, a controller operates a control element in order to bring the process variable within a target range. For example, in order to achieve a desired flow rate (process variable) a controller adjusts a valve (control element) accordingly.
One type of process control observes the quality of the product output to adjust the various process variables within the process. The quality measurement is a process variable which is measured at the output of the process. It can be difficult to control paper and pulp manufacturing processes using this technique because there is both a physical distance between the process output and a significant lag time due to the time it takes for a product to move through the process. The physical separation and the separation in time can make controlling the process to achieve a desired quality difficult.
A control system is provided for controlling a process for making paper or paper pulp. The process has a process product output at an end of the process. The controls include a process variable sensor input configured to receive a process variable related to the process. The controller is configured to provide a control signal to control the process. A process model has a model product output which is a model representation of the process product output. The model process output is a function of the sensed process variable and a product output setpoint representative of a desired process product output. The control signal is a function of the product output setpoint and the modeled product output.